March 19, 2012
By Harvey B. Simon, M.D.
Harvard Medical School
Although diet gurus have lots to say about what you should eat, few pay attention to when you should eat. It's a topic that doctors and nutritionists also tend to neglect. But that's starting to change and the results of scientific studies on eating frequency may surprise you.
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Questioning Three Square Meals a Day
For years, nutritionists (and mothers) have made three square meals the gold standard for healthy eating. But in today's busy world, it can be hard for a guy to sit down for three meals.
New research suggests that eating frequent small meals sometimes called "grazing" can be nutritionally sound. Frequent meals and snacks may even help improve weight control and cholesterol levels.
Over the years, scientists have noticed that when animals are allowed to nibble, they have lower cholesterol levels than when they are encouraged to gorge. This is true even though the total amount of food they eat is the same.
Some small previous studies with humans in a research setting have had similar findings. Now, though, a number of reports suggest that people in the real world may get similar results.
- A 2001 study of more than 14,500 British people between the ages of 45 and 75 found that people who ate six or more times a day had cholesterol levels that should reduce their cardiac risk by 10% to 20% compared with people who ate once or twice a day. And male (but not female) "grazers" were also leaner than "gorgers," even though they took in more calories.
- The French have special dietary preferences, but a 2002 study of 330 men found that those who eat more often have less body fat than those who eat less frequently. For example, the Frenchmen who ate one or two meals a day had an average body mass index (BMI) of 28.6, which put them in the overweight range. The men who ate five or more times a day were leaner. Their average BMI was 24.7 within the normal range.
Of equal importance, men who ate least often had an average waist-to-hip ratio (WHR) of 0.98, indicating excess abdominal fat and cardiovascular risk. On the other hand, the most frequent eaters had a healthier WHR of 0.93. And the results remained significant after the scientists adjusted for total caloric intake, physical activity and smoking.
- A 2003 study of 641 Massachusetts residents suggests that grazing has similar effects on this side of the Atlantic. People who ate four or more times a day were 45% less likely to be obese than those who ate three or fewer times a day. Skipping breakfast was particularly troublesome. It boosted the odds of obesity by 450%.
- A 2010 study of 1,355 Swedish men found similar results. Men who ate three or fewer times a day had significantly higher BMIs and larger waist circumferences than men who ate more than three times a day. And frequent eating appeared to protect men (but not women) from both overall obesity and excess abdominal fat, even after researchers took total caloric intake, diet quality, drinking, exercise and smoking into account.
- Back in the United States, scientists studied 257 adults to see if frequent eating might help people maintain their hard-won weight loss. In 2011 they reported that eating three meals and two snacks a day seemed to help maintain weight loss.
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What This Means for You
To be healthy, you still have to eat right and exercise regularly. But the research suggests that going hungry will not help you lose weight.
Frequent eating, either regular meals or between-meal snacks, may prevent you from overeating at mealtime. People who eat only a few times a day have elevated 24-hour insulin levels. High insulin levels promote storing energy in body fat; a high insulin level is also a marker for heart disease risk.
Still, no matter how often you eat, you have to follow the rules. Weight control really depends on simple math: If you take in more calories than you burn up, you'll gain weight. So, if you snack on the wrong food or pack in too many calories at mealtime, you'll bulk up. And if you don't exercise enough to burn off excess calories, you won't get full benefit from even the best diet.
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Learn From "Losers"
Although grazing may be better than gorging, frequent eating is not a shortcut to weight control. In fact, there is no quick fix but there is a slow fix.
The National Weight Control Registry provides information on Americans who have succeeded in losing at least 10% of body weight and who have maintained that weight loss for at least a year. Folks who have won big at the losing game share five key traits:
- They eat breakfast.
- They maintain a consistent eating pattern on weekdays and weekends.
- They weigh themselves regularly.
- They favor low-calorie, lowfat foods.
- They exercise regularly.
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Can You Split Up Your Exercise, Too?
The Harvard Alumni Study of 7,307 men (average age of 66) found that the men who got their exercise in small chunks got the same benefits as those who exercised in a few longer workouts, as long as they ended up burning the same number of calories in the course of a week.
Each volunteer reported the frequency, intensity and duration of his exercise. None of the men had heart disease when they started the study. After five years, though, 482 men had been diagnosed with heart disease. As in many earlier studies, the men who were most active enjoyed the lowest incidence of heart trouble, even after other risk factors were taken into account. But the frequency of exercise didn't influence protection one way or the other.
A study of young female college students in Wisconsin found that daily exercise was equally beneficial whether it occurred in a single 30-minute session, two 15-minute sessions or three 10-minute sessions. And in each case the benefits were substantial: In 12 weeks, the women who exercised three times a day averaged nearly 10 pounds of weight loss and also improved their cardiopulmonary fitness scores.
In addition, scientists in the United Kingdom reported similar results: Three 10-minute walks a day and one 30-minute daily walk had equally good effects on blood cholesterol level, stress and mental tension.
Finally, researchers in both the United States and England have found that bouts of exercise scattered through the day helped clear the fatty substances that enter the blood after eating as well as 30 minutes of continuous exercise.
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Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.